I. Field of the Invention
The present invention relates to fluid flow meters.
II. Description of the Prior Art
There have been a number of previously known fluid flow meters which provide an exteriorly visible signal of the fluid flow rate through the flow meter. These previously known flow meters typically include a housing having a fluid inlet, a fluid outlet and means contained in the housing to measure the fluid flow therethrough.
In one type of previously known fluid flow meter, a semi-circular vane is rotatably mounted within the housing and cooperates with a hemispherical wall section having its center offset from the axis rotation of the vane. Thus, rotation of the vane, caused by fluid flow through the flow meter, rotates the vane and creates a fluid flow passage between the outer periphery of the vane and the hemispherical wall. The cross sectional area of this fluid passage increases with the rotation of the vane so that the rotational position of the vane is indicative of the fluid flow rate through the fluid flow meter.
In still another type of previously known fluid flow meter, a piston is axially slidably mounted within a housing and includes a fluid port through which the fluid must flow from the housing inlet into the outlet. A tapered needle is positioned within this fluid port so that the axial displacement of the piston determines the cross sectional area opening of the fluid port. Fluid from through the flow meter axially displaces the piston in an amount proportional to the flow rate and this axial displacement of the piston is used to provide a signal of the fluid flow rate through the fluid flow meter.
These previously known flow meters, however, all suffer a number of common disadvantages. One disadvantage of these previously known flow meters is that they are relatively complex and therefore expensive in construction. Moreover, since these previously known flow meters include parts which move and cooperate with other parts, these flow meters require periodic disassembly and maintenance.
A still further disadvantage of these previously known flow meters is that the flow range for the flow meter is preset and non-adjustable after assembly of the flow meter. Thus, in order to obtain a flow meter with a different flow range, it is necessary to construct a separate and different flow meter.
Many of these previously known flow meters include a switch which is activated when the flow reaches a certain level and the switch, in turn, can be connected to an alarm system or other electrical system. The flow range at which the switch is actuated, however, is not easily adjustable, if adjustable at all, and is usually factory preset. Moreover, even the flow meters in which the flow rate at which the switch is actuated can be adjusted require at least partial disassembly of the flow meter.